Cream together the butter and sugars. To that add the vanilla and egg yolk. Sift together the flour and salt, and add it one cup at a time until completely incorporated. Then, by hand fold in the chocolate chips. You can do it with your mixer, but it might break the chocolate into tiny pieces.

Preheat your oven to 350.

Wrap your dough in plastic wrap and chill for at least thirty minutes. When it is chilled, roll out cookies on lightly floured parchment and bake at 350° for 10-12 minutes.